This paper points out the challenges to overcome when applying a protection strategy based on a non-selective fault clearing philosophy without DC reactors to an overhead line based multi-terminal DC grid. One of the main problems to overcome is the development of a reliable protection algorithm, which is able to discriminate both, the faulty pole and the faulty line. After a theoretical part on the initial voltage surge in phase and modal domains, a wave-front based algorithm is proposed and tested in a Multi-Terminal DC grid using Electro-Magnetic Transient software EMTP-RV. In the last section, component specifications for DC circuit breakers in OHL based DC grids are provided. Key performance indicators are applied in order to compare the performances of both conductor types while using the same protection strategy.
Pascal Torwelle, Alberto Bertinato, Bertrand Raison, Trung Dung Le, Marc Petit
Presented at 15th International Conference on Developments in Power System Protection (DPSP 2020)